N640 remark code

Remittance advice remark code N640. Remark codes add detail to the reason code on the same claim line.

Frequency limit exceeded

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What N640 means

The service has been billed more often than the payer allows within a set time period.

N640 tells you the payer counted prior claims and found this one goes over the allowed number or frequency, such as one per year or a set number of visits per period.

It typically explains a reason code like 119. The payer's count may include services billed by other providers.

Common causes

• The patient already had the service within the payer's frequency window.
• Another provider billed the same service during the period.
• Dates of service were miscounted when scheduling a repeat service.

What to do next

1. Ask the payer for the dates of the prior services it counted.
2. Check the policy's frequency rule and how it counts the period.
3. Appeal with records if a medical reason justified the extra service and the policy allows exceptions.
4. Check whether the patient signed a waiver before considering patient billing.

Related codes

• 119 (reason code) Benefit maximum reached
• N117 (remark code) Once-per-lifetime service
• N362 (remark code) Too many days or units